<!doctype html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>Mutations</title>
  <link rel="stylesheet" href="app.css">
</head>

<body>
  <div id="view"></div>
</body>

</html>
<script>
  function mutation(arr) {
    // 请把你的代码写在这里
    var str1 = arr[0].toUpperCase();
    var str2 = arr[1].toUpperCase();
    for (var index = 0; index < str2.length; index++) {
      const element = str2[index];
      if (str1.indexOf(element) === -1) {
        return false;
      }
    }
    return true;
  }

  var str = mutation(["hello", "Hello"]);
  document.getElementById("view").innerHTML = str;
  console.log(str);
</script>